Check Valve, High-Pressure Component, and High-Pressure Fuel Pump

ABSTRACT

Various embodiments include a check valve for a high-pressure component in a fuel injection system comprising: a valve housing with a valve hole having an inner diameter; a valve seat and a sealing element arranged in the valve hole; and a coil spring pushing the sealing element toward the valve seat along a longitudinal axis of the valve hole. The coil spring includes a plurality of coil turns each having an outer diameter. In a non-assembled state of the check valve, the outer diameter of at least one of the coil turns is greater than the inner diameter of at least a portion of the valve hole, so that in an assembled state of the check valve, the coil spring is secured in a force-fitting manner in the valve hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/EP2017/073412 filed Sep. 18, 2017, which designatesthe United States of America, and claims priority to DE Application No.10 2016 217 923.3 filed Sep. 19, 2016, the contents of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to fuel injection systems. Variousembodiments may include check valves for a high-pressure component in afuel injection system, high-pressure components with such a check valve,and/or high-pressure fuel pumps comprising such a high-pressurecomponent with a check valve.

BACKGROUND

High-pressure fuel pumps in fuel injection systems are used for applyinga high pressure to a fuel, wherein for example in the case of gasolineinternal combustion engines the pressure lies in a range from 150 bar to500 bar and in the case of diesel internal combustion engines thepressure lies in a range from 1500 bar to 3000 bar. The higher thepressure that can be generated in the respective fuel, the lower theemissions that are produced during the combustion of the fuel in acombustion chamber, which, in particular against the background that thereduction of emissions is becoming increasingly desirable, isadvantageous.

The fuel is in this case compressed in the high-pressure fuel pump in apressure chamber provided for this and is then usually fed by way of ahigh-pressure connection to a pressure accumulator arrangedhydraulically downstream of the pressure chamber, known as the commonrail, from where the fuel can then be injected by way of injectors intocombustion spaces of the combustion chambers. The fuel injection systemis a hydraulic system, in which passive valves such as for example checkvalves are used at various points in order only to allow the pressurizedfuel to be passed on as from a predefined pressure level. Such checkvalves may comprise outlet valves in the high-pressure connection of thehigh-pressure fuel pump, but also as pressure limiting valves, which inthe event of overpressure divert excess fuel away from the high-pressureregion of the fuel injection system in order to relieve it.

Check valves for such applications that are known from the prior art,for example from DE 10 2014 206 968 A1, are normally made up of threemain components, specifically a sealing element, a coil spring, whichpreloads the sealing element onto an associated valve seat, and a valvesecuring element, on which the helical spring is supported. This springsecuring element is normally pressed into a corresponding hole, throughwhich the fuel under high pressure is intended to be passed on.

It is however becoming increasingly more difficult to ensure a reliableinterference fit between this spring securing element and ahigh-pressure component in which this hole has been made if thepressures reside in a range of greater than 2000 bar. This is sobecause, as a consequence of the internal pressure, the high-pressurecomponent expands in the region of the hole, wherein this expansionremoves the tensioning from the interference-fit assembly and the springsecuring element begins to move around in the hole in which it is held.Then the check valve no longer functions as a valve. In addition, thespring securing element as a component itself may require an additionalinstallation space within the high-pressure component in which it isaccommodated.

SUMMARY

The teachings of the present disclosure describe check valves that maybe fastened in a high-pressure component more securely than previouslyknown. For example, some embodiments include a check valve (48) for ahigh-pressure component (44) in a fuel injection system (10), having: avalve housing (60) with a valve hole (58) formed therein, which has aninner diameter (DI) and in which a valve seat (64) and a sealing element(52) interacting with the valve seat (64) are arranged, and a coilspring (54), which keeps the sealing element (52) on the valve seat (64)by a spring force (FF) acting along a longitudinal axis (AL) of thevalve hole (58). The coil spring (54) has a plurality of coil turns (62)each with an outer diameter (DA). In a non-assembled state of the checkvalve (48) the outer diameter (DA) of at least one of the coil turns(62) is greater than the inner diameter (DI) of at least a sub-region ofthe valve hole (58), so that in an assembled state of the check valve(48) the coil spring (54) is secured in a force-fitting manner in thevalve hole (58).

In some embodiments, the coil spring (54) has a spring preloading region(68), which is deformable along the longitudinal axis (AL) under apredefined amount of force, and a force-fitting region (72), which issubstantially not deformable along the longitudinal axis (AL) under thepredefined amount of force, wherein the coil spring (54) contacts thesealing element (52) with the spring preloading region (68), while theforce-fitting region (72) is arranged opposite from the sealing element(52) along the longitudinal axis (AL).

In some embodiments, the spring preloading region (68) is formedconically and is supported with a cone tip region (70) on the sealingelement (52), wherein the force-fitting region (72) comprises aplurality of coil turns (62), which have substantially the same outerdiameter (DA), wherein in particular an outermost coil turn (62) of theforce-fitting region (72) is formed as drawn-in inwardly in thedirection of an axis of symmetry (AS) of the coil spring (53).

In some embodiments, the valve hole (58) has a first valve hole region(76) with a first inner diameter (DI1) and a second valve hole region(78) with a second inner diameter (DI2), wherein the sealing element(52) and the coil spring (54) are arranged in the first valve holeregion (76), wherein the first inner diameter (DI1) is greater than thesecond inner diameter (DI2).

In some embodiments, a bearing collar (84) on which the coil spring (54)is supported with its force-fitting region (72) is formed at atransition (82) from the first valve hole region (76) to the secondvalve hole region (78).

In some embodiments, the first inner diameter (DI1) is substantiallyconstant at least along a longitudinal extent (L) of the coil spring(54), wherein the second inner diameter (DI2) widens conically along thelongitudinal axis (AL) away from the first valve hole region (76).

In some embodiments, a transition (82) from the first valve hole region(76) to the second valve hole region (78) is formed as convexly rounded.

As another example, some embodiments include a high-pressure component(44), in particular a high-pressure connection (46) for a high-pressurefuel pump (18), having a check valve (48) as described above,characterized in that the valve housing (60) is formed by thehigh-pressure component (44).

As another example, some embodiments include a high-pressure fuel pump(18) for a fuel injection system (10) of an internal combustion engine,having a pressure chamber (26) for applying high pressure to fuel (12),and a high-pressure component (44), which is arranged downstream of thepressure chamber (26) and has a check valve (48) as described above,which is formed in particular as an outlet valve (28) for letting outfuel (12) under high pressure from the pressure chamber (26).

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the teachings herein are explained in more detailbelow on the basis of the accompanying drawings, in which:

FIG. 1 shows a schematic representation of a fuel injection system foran internal combustion engine that has a high-pressure fuel pump with atleast one check valve;

FIG. 2 shows a schematic longitudinal sectional representation throughthe high-pressure fuel pump from FIG. 1 with a high-pressure connectionas a high-pressure component;

FIG. 3 shows a sectional view of a high-pressure component with a checkvalve from the prior art;

FIG. 4 shows a sectional view of a first embodiment of a high-pressurecomponent with a check valve incorporating the teachings herein;

FIG. 5 shows a sectional view of a coil spring of the check valve fromFIG. 4;

FIG. 6 shows a perspective representation of the coil spring from FIG.5;

FIG. 7 shows a sectional view of a second embodiment of a high-pressurecomponent with a check valve incorporating the teachings herein;

FIG. 8 shows a view of a detail of the high-pressure component from FIG.7; and

FIG. 9 shows a sectional view of a third embodiment of a high-pressurecomponent with a check valve incorporating the teachings herein.

DETAILED DESCRIPTION

In some embodiments, a check valve for a high-pressure component in afuel injection system has a valve housing with a valve hole formedtherein, which has an inner diameter and in which a valve seat and asealing element interacting with the valve seat are arranged, and a coilspring, which keeps the sealing element on the valve seat by a springforce acting along a longitudinal axis of the valve hole. The coilspring has a plurality of coil turns each with an outer diameter. In anon-assembled state of the check valve, the outer diameter of at leastone of these coil turns is greater than the inner diameter of at least asub-region of the valve hole, so that in an assembled state of the checkvalve the coil spring is secured in a force-fitting manner in the valvehole.

In some embodiments, it is possible by contrast with the prior art todispense with the valve securing element, because the coil spring itselfestablishes the force-fitting connection to the high-pressure component,and consequently there is no need for the spring securing element. As aresult, negative influences such as pressure infiltration of theinterference fit of the spring securing element and the high-pressurecomponent are avoided. What is more, the elimination of the interferencefit has the effect of increasing the high-pressure resistance of thehigh-pressure component. In addition, installation space which in theprior art is provided for the spring securing element can be saved.

In some embodiments, the coil spring has a spring preloading region,which is deformable along the longitudinal axis under a predefinedamount of force, and a force-fitting region, which is substantially notdeformable along the longitudinal axis under the predefined amount offorce. In this case, the coil spring contacts the sealing element withthe spring preloading region, while the force-fitting region is arrangedopposite from the sealing element along the longitudinal axis.

The coil spring is accordingly formed in such a way that one regionthereof is optimized for providing the necessary spring force to keepthe sealing element on the valve seat, and that a region separatetherefrom is optimized for providing the securement to preventdisplacement of the coil spring in the high-pressure component. Withsuch an optimized coil spring, the problem of component deformation thatoccurs with a spring securing element due to the infiltration of theinterference fit can be advantageously avoided, because it is simplypossible to dispense with the spring securing element since the coilspring itself undertakes the securement in the high-pressure component.This coil spring is therefore geometrically adapted in such a way thaton the one hand it undertakes the spring preloading of the sealingelement in the spring preloading region, and on the other hand it isdesigned in the force-fitting region in such a way that the securementto prevent displacement in the high-pressure component is ensured.

In some embodiments, in the spring preloading region the individual coilturns are formed as spaced apart from one another, so that the coilspring in this region can be deformed along the longitudinal axis when apredefined amount of force is applied to the coil spring. This may takeplace for example by pressure being applied by the sealing element. Itis also advantageous if in the force-fitting region the coil turns liedirectly against one another, without a spacing in between, so that nodeformation of the force-fitting region is possible by the amount offorce that can deform the spring preloading region. In some embodiments,the spring preloading region is in this case formed conically and issupported with a cone tip region on the sealing element.

In some embodiments, the cone tip region with which the coil spring issupported on the sealing element has a conical widening, in order to bebetter able to engage around the sealing element and consequently guideit. In some embodiments, the force-fitting region comprises a pluralityof coil turns, which have substantially the same outer diameter. Byproviding a number of coil turns that have the same outer diameter, itis possible to be able to establish a secure force fit with the valvehole.

In some embodiments, an outermost coil turn of the force-fitting regionis formed as drawn-in inwardly in the direction of an axis of symmetryof the coil spring. As a result, a point of engagement for a tool can beprovided on the coil spring by an inwardly protruding end, in order toallow the coil spring to be handled and reliably introduced into thevalve hole. At such an end, the coil spring can be turned counter to itswinding direction by means of a tool after being placed into the valvehole during a joining operation. The tool transfers a torque by engagingin this outermost drawn-in coil turn of the coil spring. As a result,the outer diameter of the force-fitting region is reduced, and the coilspring can be pushed into the valve hole in a defined manner. If thetorque from the tool that is used is then removed again, the coil springopens out again and lies firmly against the high-pressure component inthe valve hole, whereby the coil spring is then fixed by means of aforce fit.

Altogether, the coil spring is therefore deformable in the radialdirection in particular in the force-fitting region, in order to be ablein this way to reversibly and temporarily change the outer diameter.

In some embodiments, the valve hole has a first valve hole region with afirst inner diameter and a second valve hole region with a second innerdiameter, wherein the sealing element and the coil spring are arrangedin the first valve hole region. The first inner diameter in this casemay be greater than the second inner diameter. In some embodiments, abearing collar on which the coil spring is supported with itsforce-fitting region is in this case formed at a transition from thefirst valve hole region to the second valve hole region. In someembodiments, the valve hole is therefore provided with a geometry tosecure the coil spring additionally against displacement in the axialdirection by means of a form fit.

In some embodiments, the first inner diameter is substantially constantat least along a longitudinal extent of the coil spring. The secondinner diameter widens conically along the longitudinal axis away fromthe first valve hole region. In some embodiments, a transition from thefirst valve hole region to the second valve hole region is formed asconvexly rounded. The conical widening can provide an insertion cone oran insertion radius, by way of which the coil spring can be insertedinto the valve bore. During insertion, it can then easily slide over theconvex rounding between the two valve hole regions, to then lie firmlyagainst the bearing collar in the first inner diameter of the valvehole. The coil spring is pushed into the valve hole by way of theinsertion cone provided by the conical widening or an insertion radiusand then, after passing over the bearing collar, opens out.

In some embodiments, a high-pressure component, which is formed forexample as a high-pressure connection for a high-pressure fuel pump, hasa check valve described above, wherein the high-pressure componentitself forms the valve housing of the check valve.

In some embodiments, a high-pressure fuel pump for a fuel injectionsystem of an internal combustion engine has a pressure chamber forapplying high pressure to fuel and a high-pressure component which isarranged downstream of the pressure chamber and has the check valve asdescribed above. The check valve may in this case be arranged forexample in a high-pressure connection and be formed as an outlet valvefor letting out fuel under high pressure from the pressure chamber.However, it is also possible that the check valve is formed as apressure limiting valve, in order to divert high pressure in a pressureaccumulator region arranged downstream of the pressure chamber.

Altogether, the check valve described above allows the number ofcomponents to be reduced while maintaining the same function of thecheck valve. In addition, the previously customary interference-fitassembly is no longer needed, whereby a reduction of the stresses in thehigh-pressure component is made possible. Furthermore, the pressure dropacross the check valve due to the previously provided and now absentspring securing element is also reduced.

FIG. 1 shows a schematic representation of a fuel injection system 10 ofan internal combustion engine, which delivers a fuel 12 from a tank 14by way of a primary pump 16, a high-pressure fuel pump 18, and ahigh-pressure fuel accumulator 20 to injectors 22, which then inject thefuel 12 into combustion spaces of the internal combustion engine. Thefuel 12 is introduced into a pressure chamber 26 by way of an inletvalve 24 on the high-pressure fuel pump 18 and let out from thispressure chamber 26 by way of an outlet valve 28 and passed on to thehigh-pressure fuel accumulator 20.

FIG. 2 shows a longitudinal sectional representation of thehigh-pressure fuel pump 18 from FIG. 1. Arranged in a housing 30 of thehigh-pressure fuel pump 18 are a number of bores 32, which assumevarious functions. By way of an inlet bore 34, the fuel 12 is fed from adamper 36 to the pressure chamber 26, in which a plunger 38 moves in atranslatory manner in a plunger bore 40 and thus periodically compressesthe fuel 12 in the pressure chamber 26. The compressed fuel 12 is thenpassed on by way of an outlet bore 42 into a high-pressure component 44,known as the high-pressure connection 46, from where the fuel 12 is thenpassed on further to the high-pressure fuel accumulator 20.

In order to ensure that only fuel 12 under the desired pressure reachesthe high-pressure fuel accumulator 20, normally arranged in thehigh-pressure component 44 is the outlet valve 28, which is usuallyformed as a check valve 48. Often also arranged in this region is asecond check valve 48, in order to be able to divert an overpressure inthe high-pressure fuel accumulator 20 back again for example into thepressure chamber 26 or into a low-pressure region 50 of the fuelinjection system 10.

FIG. 3 shows a sectional view of a high-pressure component 44 of such ahigh-pressure fuel pump 18 from FIG. 2, wherein such a check valve 48from the prior art is arranged in the high-pressure component 44. Thecheck valve 48 has a sealing element 52, a coil spring 54 and a springsecuring element 56. The spring securing element 56 is fixed with aninterference fit in the outlet bore 42, which at the same time forms avalve hole 58. It serves the purpose of allowing the coil spring 54 tobe supported on it, and of preventing the coil spring 54 from movingwithin the valve hole 58.

In the case of modern high-pressure fuel pumps 18, in the meantime veryhigh pressures are generated in the fuel 12, and these also have aneffect on the spring securing element 56. This is so because these highpressures have the effect that the valve hole 58 widens, andconsequently the spring securing element 56 can no longer be keptsecurely in the valve hole 58 by the interference-fit assembly.Therefore, there now follows a proposal of a formation of a check valve48 in which it is possible to dispense with this spring securing element56 with the known disadvantages at very high pressures in the fuel 12.

FIG. 4 shows in this respect a sectional representation of an exampleembodiment of such a check valve 48. Since the outlet bore 42 at thesame time forms the valve hole 58 for the check valve 48, thehigh-pressure component 44, in which the check valve 48 is arranged,also forms at the same time a valve housing 60 for the check valve 48.The first embodiment in FIG. 4 completely dispenses with the springsecuring element 56 and other bearing surfaces on which the coil spring54 could be supported, since the geometry of the valve hole 58 and thegeometry of a sub-region of the coil spring 54 are made to match oneanother in such a way that the coil spring 54 supports itself on thevalve hole 58. For this purpose, the coil spring 54 has a plurality ofcoil turns 62, which each have an outer diameter DA. When the coilspring 54 has not yet been introduced into the valve hole 58, this outerdiameter DA of at least one of these coil turns 62 is greater than aninner diameter DI of the valve hole 58, to be precise at least in asub-region of the valve hole 58. If the coil spring 54 is thereforecompressed slightly in the radial direction in order to be inserted intothe valve hole 58, and then let go, the coil spring 54 expands in theradial direction as soon as it is arranged in the valve hole 85, andpresses itself against the valve hole 58 with its coil turns 62 thathave the great outer diameter DA, and consequently anchors itself in thevalve hole 58.

If forces due to the pressurized fuel 12 then act along a longitudinalaxis AL of the valve hole 58 from the sealing element 52, which the coilspring 54 is keeping on a valve seat 64 formed in the valve hole 58, itis then no longer the case that widening of the valve hole 58 undoes theinterference-fit assembly of a previously known spring securing element56. This is so because the coil turns 62 also expand, and consequentlykeep themselves firmly against the valve hole 58′ specifically due tothe high force effect. The coil spring 54 can therefore keep the sealingelement 52 on the valve seat 64 even under high pressures and withundiminished spring force FF.

FIG. 5 shows a sectional view through the coil spring 54 from FIG. 4. Itcan be seen that the coil spring 54 has two regions, which havedifferent functions. A spring preloading region 68, which in the fittedstate is supported on the sealing element 52, is provided for applyingthe spring force FF to the sealing element 52. For this purpose, theindividual coil turns 62 are formed as slightly spaced apart from oneanother, in order to allow a deflection distance in the direction of thelongitudinal axis AL. In this region, the coil spring 54 is deformablealong the longitudinal axis AL as soon as a sufficient predefined amountof force is applied to the coil spring 54, for example when pressurizedfuel 12 presses on the sealing element 52 from the other side.

As can be seen in FIG. 5, this spring preloading region 68 isadvantageously conically formed and during operation is supported with acone tip region 70 on the sealing element 52. The coil spring 54 alsocomprises a force-fitting region 72, directly adjoining the springpreloading region 68 and consequently lying opposite from the sealingelement 52 during operation. In this force-fitting region 72, the coilturns 62 lie directly against one another, so that here the coil spring54 is not deformable along the longitudinal axis AL when the predefinedamount of force acts for example from the sealing element 52 on the coilspring 54. The force-fitting region 72 has a number of coil turns 62,all of which have the same outer diameter DA, which in the non-assembledstate is greater than the inner diameter DI of the valve hole 58.Therefore, the coil spring 54 goes over from its conical form in thespring loading region 68 into a cylindrical form in the force-fittingregion 72.

FIG. 6 shows a perspective view of the coil spring 54 from FIG. 5. Hereit can be seen that the outermost coil turn 62 is formed as drawn-ininwardly in the direction of an axis of symmetry AS of the coil spring54, about which all of the coil turns 62 of the coil spring 54 aresymmetrically arranged. This creates an end 74, at which the coil spring54 can be engaged by a tool. By means of such a tool, for example byturning, the outer diameter DA of the coil spring 54 in theforce-fitting region 72 can be changed, so that the coil spring 54 canbe inserted into the valve hole 58. If the tool is then removed again,the coil spring 54 expands again in the force-fitting region 72, and aforce fit is established between the coil spring 54 and the valve hole58. By way of the end 74, therefore, a joining torque can be applied tothe coil spring 54 by means of an assembly tool.

FIG. 7 shows a sectional representation of the high-pressure component44 with the check valve 48 in another example embodiment. Here it can beseen that the valve hole 58 has a first valve hole region 76, in whichthe sealing element 52 and the coil spring 54 are arranged. The valvehole 58 also has a second valve hole region 78, which adjoins the firstvalve hole region 67 downstream along the longitudinal axis AL as seenfrom the sealing element 52. A first inner diameter DI′ of the firstvalve hole region 76 is greater than a second inner diameter DI2 of thesecond valve hole region 78. As a result, a bearing collar 84, on whichthe coil spring 54 is supported with its force-fitting region 72 in theassembled state, is formed at a transition 82 between the two valve holeregions 76, 78.

FIG. 8 shows the high-pressure component 44 from FIG. 7 in an enlargedrepresentation in the region of the force-fitting region 72 of the coilspring 54. It can be seen that the first inner diameter DI′ of the firstvalve hole region 76 is substantially constant, since a secure force fitcan in this way be achieved between the coil spring 54 and the valvehole 58. Therefore, the inner diameter DI′ is substantially constant, atleast along the longitudinal extent, that is to say the length L, of thecoil spring 54. In order to insert the coil spring 54 more easily intothe valve hole 58, the second inner diameter DI2 widens conically alongthe longitudinal axis AL away from the first valve hole region 76. Aninitially flat insertion cone, which further widens conically in thedownstream direction, is shown in FIG. 8.

FIG. 9 shows a sectional view through a third embodiment of thehigh-pressure component 44, in which the second inner diameter DI2conically widens greatly after the first inner diameter DI1, andconsequently forms a steep insertion cone. In addition, in FIG. 9 thereis formed at the transition 82 an insertion radius, in which thetransition 82 is formed as convexly rounded. Also as a result of this,facilitated insertion of the coil spring 54 into the valve hole 58 canbe achieved.

What is claimed is:
 1. A check valve for a high-pressure component in afuel injection system, the check valve comprising: a valve housing witha valve hole formed therein, the valve hole having an inner diameter; avalve seat and a sealing element interacting with the valve seatarranged in the valve hole; and a coil spring pushing the sealingelement toward the valve seat with a spring force acting along alongitudinal axis of the valve hole; wherein the coil spring includes aplurality of coil turns each having an outer diameter; and in anon-assembled state of the check valve, the outer diameter of at leastone of the coil turns is greater than the inner diameter of at least aportion of the valve hole, so that in an assembled state of the checkvalve, the coil spring is secured in a force-fitting manner in the valvehole.
 2. The check valve as claimed in claim 1, wherein: the coil springincludes: a spring preloading region deformable along the longitudinalaxis under a predefined amount of force, and a force-fitting regionsubstantially not deformed along the longitudinal axis under thepredefined amount of force; and the coil spring contacts the sealingelement in the spring preloading region and the force-fitting region isarranged opposite from the sealing element along the longitudinal axis.3. The check valve as claimed in claim 2, wherein: the spring preloadingregion comprises a conic shape supported by a cone tip region on thesealing element; the force-fitting region comprises a portion of theplurality of coil turns which have substantially the same outerdiameter; and an outermost coil turn of the force-fitting region isdrawn-in inwardly in the direction of an axis of symmetry of the coilspring.
 4. The check valve as claimed in claim 1, wherein: the valvehole has a first region with a first inner diameter and a second regionwith a second inner diameter; the sealing element and the coil springare arranged in the first region; and the first inner diameter isgreater than the second inner diameter.
 5. The check valve as claimed inclaim 4, further comprising a bearing collar on which the coil spring issupported with its force-fitting region formed at a transition betweenthe first region to the second region.
 6. The check valve as claimed inclaim 4, wherein: the first inner diameter is substantially constant atleast along a longitudinal extent of the coil spring; and the secondinner diameter widens conically along the longitudinal axis away fromthe first region.
 7. The check valve as claimed in claim 4, wherein atransition from the first region to the second region is convexlyrounded.
 8. A high-pressure component, for a high-pressure fuel pump,the component comprising: a valve housing formed by the high-pressurecomponent, the valve housing with a valve hole formed therein, the valvehole having an inner diameter; a valve seat and a sealing elementinteracting with the valve seat arranged in the valve hole; and a coilspring pushing the sealing element toward the valve seat with a springforce acting along a longitudinal axis of the valve hole; wherein thecoil spring includes a plurality of coil turns each having an outerdiameter; and in a non-assembled state of the check valve, the outerdiameter of at least one of the coil turns is greater than the innerdiameter of at least a portion of the valve hole, so that in anassembled state of the check valve, the coil spring is secured in aforce-fitting manner in the valve hole.
 9. A high-pressure fuel pump fora fuel injection system of an internal combustion engine, the fuel pumpcomprising: a pressure chamber for applying high pressure to fuel; ahigh-pressure component arranged downstream of the pressure chamber; anda check valve comprising an outlet valve for letting fuel out of thepressure chamber under high pressure; the check valve comprising: avalve housing formed by the high-pressure component, the valve housingwith a valve hole formed therein, the valve hole having an innerdiameter; a valve seat and a sealing element interacting with the valveseat arranged in the valve hole; and a coil spring pushing the sealingelement toward the valve seat with a spring force acting along alongitudinal axis of the valve hole; wherein the coil spring includes aplurality of coil turns each having an outer diameter; and in anon-assembled state of the check valve, the outer diameter of at leastone of the coil turns is greater than the inner diameter of at least aportion of the valve hole, so that in an assembled state of the checkvalve, the coil spring is secured in a force-fitting manner in the valvehole.